A stereoscopic camera is ordinarily designed to take two photographs of the subject in front of it. The photographs are taken from viewpoints separated by substantially the same distance as a pair of normal human eyes. When the subsequent positive prints are looked at through a suitable stereoscopic viewer they combine to give a three-dimensional reproduction of the subject that was photographed.
Stereo cameras using 35 mm. film can take pairs of 24.times.30 mm. pictures which are separated on the filmstrip by one frame, i.e. one imaging area. The filmstrip is advanced one frame and three frames alternately by use of a special film transport.
Normal 35 mm. cameras making conventional full-frame 24.times.36 mm. exposures can also be used for stereo work with the aid of a stereo attachment accessory. This splits up the 24.times.36 mm. imaging area to produce two half-frame 18.times.24 mm. exposures forming a matched stereo pair. One way in which this is done is for the stereo attachment accessory to have a pair of spaced-apart frontal lenses which face the subject to be photographed and a pair of juxtaposed rear lenses located in front of the taking lens of the camera. Light rays reflected from the subject are received through the two frontal lenses, then reflected from a first pair of reflectors towards one another to a second pair of reflectors, and then reflected through the rear lenses to the taking lens and to respective half-frame imaging areas on the filmstrip. See prior art U.S. Pat. No. 3,815,970, issued Jun. 11, 1974.
A stereo camera that has three taking lenses for making three half-frame exposures is disclosed in prior art U.S. Pat. No. 5,294,951, issued Mar. 15, 1994. The two endmost lenses are separated from one another by substantially the same distance as a pair of normal human eyes.
Commonly assigned U.S. Pat. No. 5,189,453 issued Feb. 23, 1993 discloses a method and apparatus for pre-exposing the same image of a distinctive mark, figure or the like on one corner-portion of each full-frame imaging area on a filmstrip pre-loaded in a single-use camera. According to the disclosed method, diffuse light is first projected through an image-bearing transparency to the taking lens of the camera and then to a relatively small corner portion of respective imaging areas on the filmstrip. Thus, a latent image of the distinctive mark, figure or the like is exposed on one corner portion of each imaging area of the filmstrip without exposing the remainder of each imaging area. When the camera is subsequently used to take pictures, the exposures are made on the same imaging areas over the latent images that were pre-exposed on the filmstrip.
No suggestion is made in U.S. Pat. No. 5,189,453 to somehow use the disclosed method for stereoscopic picture-taking.